Chart Watch is 17 Tracks’ weekly look at the happenings on the Billboard Hot 100 with chart expert Hunter Schwarz.

After spending a single week at the summit, Rihanna’s “S&M” featuring Britney Spears slides to No. 4 as Katy Perry’s “E.T.” featuring Kanye West retakes the No. 1 position with an impressive burst of sales and radio airplay.

In my last Chart Watch column, I compared the battle between Perry/West and Fenty/Spears to a presidential campaign, and likened Spears to the Sarah Palin of pop. Those comparisons aren’t that far off. Def Jam’s last minute decision to add Spears to “S&M” was a calculated Hail Mary. The label correctly assumed that by courting Britney’s rabid fan base, the song could finally break from its No.2 position and overtake “E.T.”

Remember when McCain picked Palin and suddenly, the disgruntled Republican base had someone to cheer for on the ticket? Yeah, it’s kind of like that.

And just like the Palin effect eventually wore in the polls, so has the Spears effect. The new version of “S&M” experienced a 46 percent slip in sales and lost its top spot on radio songs. On the Hot 100, this equated to a 1-4 slide. Spears and Jive seem to be wasting no time worrying about the drop, releasing their own remix, the Femme Fatale mix of “Till The World Ends” featuring tourmate Nicki Minaj and song co-writer Ke$ha. Britney is ”Going Rogue.” I have a feeling that by summer’s end, these star studded remixes will be a full-on trend.

“E.T.,” as I’ve written before, is doing astonishingly well for a fourth single from an eight-month-old album. Of course, the addition of West on the track helps, pulling in his fans as well as Perry fans who already purchased Teenage Dream last year. Even without that, however, the song has become a monster. Thanks to a performance on American Idol, the song had its best sales week ever, with 344,000 downloads. The track also jumped to the top slot on radio. Love it or hate it, “Kiss me, ki-ki-kiss me” is the pop equivalent of “hope and change.” It’s resonating with listeners.

The rest of the field of female pop stars who are dominating the charts right now seem to be underperforming. Both Britney Spears’ “Till The World Ends” and Lady Gaga’s “Judas” drop out of the top 10. This is despite an airplay increase for both songs and a sales increase for Spears. The sales of the Minaj/Ke$ha assisted-remix will reflect in next week’s chart, and one wonders if Interscope will pressure Gaga to team up with someone for “Judas.” If Gaga can get away with dressing like a motorcycle on her album cover, something tells me she won’t be willing to cash in on the team up remix craze, but who knows, she might be more willing if its with someone she’s already worked with twice before. Beyonce would probably oblige.

Following the No. 1 debuts of both Britney and Gaga’s lead singles, it seemed a given that Colombia would try and do the same for Beyonce. Instead, her new single, “Run The World (Girls),” debuts at an embarrassing (for her) No. 33. Perry can breathe easy knowing she can keep the No. 1 spot another week. Well, at least for American artists.

The song threatening “E.T.” the most isn’t another dance pop song or a song with featuring credits, it’s actually Adele’s “Rolling In The Deep.” The British crooner’s hit moves 6-2, and like “E.T.,” it can thank American Idol. Contestant Haley Reinhart performed the song on last week’s show, prompting a 99 percent increase in sales while radio airplay rose as well. It seems the American public is catching on that Adele is someone worth listening to. While that’s her greatest strength right now, it could also hurt her on the Hot 100. Her sophomore album, 21, returns to the No. 1 spot on the Billboard 200 album chart. If consumers are convinced Adele is good enough, they might opt for buying her album instead of a few songs.

Here’s what’s happening on the rest of the Hot 100:

I thought the Black Eyed Peas were done for after their awful Super Bowl performance failed to energize sales of their latest album. They’re doing something right with “Just Can’t Get Enough” though as the song moves up to No. 3.

Tine Tempah moves to his highest spot ever in the U.S. as “Written In The Stars” climbs to No. 13.

Taylor Swift enters the top half of the Hot 100 with “Mean.” The song moves 51-50 this week, and Swift recently tweeted that the video was on its way.